With a pressure gauge on it reads 2200psi hit the brakes it drops to 700psi and the light comes on.
Do your brakes work....I don't think I've ever been in a Volvo loader that didn't give a brake pressure warning. My L70 gave me a BP warning when I started it this morning. It stays on until I start driving. I let it warm up for about 20 min because of the cold. Sometimes when I get back in, I have an injection system failure message, and it will go into limp mode. I just shut it down, and re-start, and I am on my way. I am a big fan of Volvo equipment, but I do find that there are always codes. 99% of the time they are harmless, but my L70, and the 4 L90s are all the same.
They do work, but unless your very easy on the pedal they almost lock up. Everything is pointing to the brake accumulators.
You're sure to get a helpful reply. Just depends how busy everyone is. We mostly get the dealer to do anything like that where I work. They figured out years ago, that for the price, it's faster. Our mechanics just do service, small repairs, and emergency stuff. I actually saw the Cat man working on their 1984 D7G this summer. Hope you figure it out.
You should get 4+ presses of the brakes to drop that much pressure . Does it hold accumulated pressure with the engine off ? It could be accumulators but they are usually fairly reliable . If they come off easy , check them with a portapower pump and pressure guage . You are not leaking into one of the axles?
The pressure leaks of slowly with the engine. If you hit the brakes one time with the engine off pressure goes to zero.
bad accumulator, remove-check and repair...